1. Field of the Invention
This invention is related to a coin selector which accurately judges whether a coin is genuine or false by increasing a distinguishing accuracy of measuring the thickness of a coin and more particularly is suitable for bimetal coins which are made up of different material either at the center or the rim of the coin.
2. Description of Related Art
Coin selectors which distinguish between genuine and false coins have used a material detecting coil, a thickness detecting coil and a diameter detecting coil located along a coin passageway such shown in as Japan laid-open patent application 200-187746. The thickness detecting coil and the material detecting coil are located relatively to the center of the coin and the diameter detecting coil is located relatively to the rim of the coin.
Therefore, the thickness of a false coin with comparable material and diameter may pass through, because machining a false coin's center is easy to do. To prevent such false coins, a bimetal coin which has a circular center fitted into a rim ring has been suggested.
Accordingly, the center disc and the rim ring are made up of different material. Therefore, distinguishing of the coin's material can increase the accuracy. However, the prior art cannot increase such accuracy when a thickness sensor unit is located to refer to the center of the coin.
When a coin uses the same center material and rim material, it is difficult to distinguish authenticity.
U.S. Pat. No. 4,323,148 represents one approach to distinguish false coins.
The prior art is still seeking to improve coin selectors.